Brake mechanism



vJune 23, 19212.'l H. w. LINDSAY BRAKE-MECANISM Filed Septif29, 14941 2Sheets-Smet l June 194.2- H.'w. LINDSAY 2,287,438

BRAKE MEcHANlsM Filed sept. 29, 1941 zAsheets-sheetlz l\\\\\\\\ I. E

Patented June 2319'42 UNITED STATES PATENT" oFFlcE A BRAKE MECHANISMHorace W. Lindsay, La Porte, Ind., assigner to Allis-ChalmersManufacturing Company, Milwaukee, Wis., a corporation of DelawareAppupmpp september 2s, 1941, sei-al Np. riesco 9 Claims. (Cl. 37156)This invention relates in general to improvements in brake mechanismsand more particularly to a braking system for a motor vehicle comprisingat least one driving wheel mounted on a member pivotally attached tothevehicle frame, the system being so arranged as to prevent excessiverocking oi the pivoted member in response to variable degrees ofapplication of the brakes.

The .braking system of motor vehicles generallycomprises brakes `actingon the driving wheels,

. which frequently cooperate with brakes acting on idler wheels,The'brakes on the driving wheels should be able to prevent the wheelsfrom turn-' ing under the action both of the momentum of the vehicle andof the lmotor torque. This requirement is in prevision of the fact thatthe motor may be left in gear with the throttle open, eitherinadvertently ,or by accident.

Under such conditions, considerable efforts of the tandem drive type bymeans of which the are transmitted through the driving wheels, and

if the wheels are mounted on arms which are pivotally attached to thevehicle frame, the arms tend to rock excessively under the action of thebraking eiorts. This effect is particularly objectionable in vehiclesprovided with a tandem drive in which the driving wheels are mounted onbalance arms, generally called tandem cases, which are pivotedy aboutthe driving axle. The

tandem cases are-generallyv maintained in position by the sole action ofthe vehicle weight, and the braking eiorts may rock the tandem cases tothe point of causing the entire tandem assembly to turn over.

` This disadvantage may ing the propulsion system of the vehicle with avdual braking system such that, at least when the brakes are locked, thetandem cases are prevented from rocking with respect to the vehicleframe. This result may be obtained by providing a brake acting betweenthe propulsion system and the tandem cases and another suitablydimensioned brake acting between the propulsion system and the mainframe of the vehicle.

Itis therefore one object oi the present invention to provide a brakingsystem for a motor vehicleso arranged as to prevent braking efforts fromimparting excessive rocking motion to a driving wheel arm pivotall'ymounted on the vehicle frame. v

Another object of the present invention is to provide a braking systemfor a motor vehicle comprising a brake tending to cause a wheel arm to`rock about one axisV and another brake be obviated by providheight ofthe moldboard will remain undis- Lubed upon severe application of thebrakes.

Objects and advantages other than those above set forth will be apparentfrom a consideration of the following description when read inconnection with thq accompanying drawings, in' which:

Fig. l is a view partly in side elevation and partly in section oi aroad grader comprising a tandem drive provided with a braking systemarranged in accordance with the present invention;

Fig. 2 is an enlarged view, partially in cross section, of a portion ofthe grader illustrated in Fig. l 'showing the propulsion system and thedifferent brakes of the grader;

3 is a plan View partially in cross section showing the propulsionsystem and the different brakes of the grader;

Fig. 4 is a view in elevation of the braking system of the grader;

Fig. 5 is a plan view of the grader;

Fig. 6 is a view in longitudinal cross section the braking system ofAthrough the transmission brake actuating cylinder;

Fig."8 is an enlarged view in cross section of the control valvesincluded in the system illustrated in Fig. 5; and

Fig. 9 is an enlarged plan view of the sliding yoke `connecting theparking brake lever with the transmission brake or the grader.

Referring more particularly to the drawings by characters of reference,the grader illustrated in Fig. 1 has for its principal component awheeled frame Il. This frame comprises a forward tubular portion i2supported on a pair of front idler'wheels I3, and a rear box-likeportion I4 containing the engine I5 and supported on two pairs ofdriving wheels i6, Il mounted in l OII Shaft 23.

As shown more clearly in Fig. 2, the propulsion system for the gradercomprises engine I5, wheels I6, I1 and suitable transmission meanstherebetween. 'I'he transmission means comprise a clutch 24, atransmission 25, and a final drive 26. Transmission 25 may be of anysuitable known type comprising a plurality of suitable groups of gearssplined on a plurality of shafts, including a shaft 21 provided with abrake 26. The bottom shaft of the transmission is geared to the finaldrive of the transmission which comprises a divided driving axle 29.

The axle is journaled in frame portion I4 and carries two pairs ofsprockets 3|, 32. Sprockets 3| drive wheels I6 through chains 33 andthrough spockets 34 moimted on theaxles 35 of wheels I5. Sprockets 32similarly drive wheels I1 through chains 36 and through sprockets 31mounted on the wheel axles 38. The driving wheels are mounted on balancearms or tandem cases 39 servingv as housings for the sprockets andchains. To enable the wheels to follow the contour of the ground, thetandem cases are pivotally mounted on frame II through axle 29, whichtransmits the weight of the rear portion of the grader to the drivingwheels through the tandem cases. At least wheels vI6 are provided withbrakes 4| of any suitable type.

Brakes 4| are preferably lof the hydraulically operated internalexpanding type shown in detail in Fig. 4 of the drawings. Each wheelbrake accordingly comprises a brake drum 42 mounted on one of the wheelsand a pair of brake shoes 43 mounted on a backing plate 44. Thebac-king' plate is rigidly mounted on the corresponding tandem case andcarries a hydraulic actuat-` ing cylinder 45. The cylinders areconnected through piping 46 with a. master cylinder 41.

close proximity to the driving axle to prevent its being vdamaged ybyrocking of the tandem lcases relatively. tothe frame.

Brake 26 is preferably of the disk type comarising a'- disk 4s siidsbiyspiined on shaft 21.`

Disk 49 is adapted to be'clamped between an inner pressure plate rigidlymounted on the transmission housing andl a movable outer pressure plate52. Plate 52 may be urger toward plate 5| by means of a ,lever 53fulcrumed on the brake housing through a pin 54. '4 Lever 53 may beactuated by a piston 55 movable in a cylinder 56 connected with mastercylinder "through piping 51. Piston 55 and lever 5 3 are connectedthrough a piston rod 56 abutting against adepression o f the outer faceof the piston without being attached thereto.V Cylinder 56 -may beprovided with the usual bleedery screw 59 to permit removal of any airentrapped within the cylinder'. v

Piping 51 may comprise an adjustable check valve 6| for connectingcylinder 56 with master cylinder 41 only in response to increase of thebrakingv effort exerted by the wheel brakes beyond a-' predeterminedadjustable value. Valve cause they are interconnected by means of chains33, 36 and of axle 29. The braking action is the saine ln principlewhether the brakes be slipping or,` locked, lonly the magnitude of thebraking effort being predetermined by the brake shoe pressure as long asthe brakes remain slipping.

The brakes may therefore be assumed to belocked and the tandem system ofwheels I6, I1 and tandem cases 39 maythen be considered as constitutinga single solid body. This body is subjected to two forces. One force isthe weight of the tandem system itself and of the portion of the gradersupported thereon, which weight tends to maintain all driving wheelsapplied to the ground. The other force is the force of inertia havingits point of action at the driving axle and resulting from thedeceleration of the entire grader. The latter force tends to rock theentire tandem system about an axis passing through the points of contactof wheels I6 with f the ground. Under unfavorable circumstances,

as when wheels I6 are dropped into a ditch, this force may causethetandem system to turn over completely.

force of inertia again tends to rock the tandem cases against thestabilizing action of the weight of the vehicle, but the conditionsbecome somewhat dierent from those considered above. The transmissionbrake, when locked, holds the driving axle 29 immovable with respect tothe vehicle frame, but the wheelsl remain free to turn with' respect tothe tandem cases. If sprockets 3|, 34 have the same diameter, thesprockets with chains 33 and axle 29 become the mechanical equivalent ofan articulated. parallelogram linkage connecting the wheels directlywith the frame. As the frame remains substantially level when the tendemcases rock, the driving wheels retain substantially theiroriginalangular position regardless of any rocking of the tandem cases.Such rocking then must take place about an axis which is that oftheaxles of wheels I6. If sprockets 3| have a smaller diameter thansprockets 34, as shown in thedrawing, the axis of rotation is depressedbelow the axis of wheels I6 to an extent depending upon the sprocketratio.

Assuming valves 6|, 62 omitted from the braking system, depressing brakepedal 48 causes all three brakes to be applied simultaneously. As longasthe braking. eort is moderate and the brakes are slipping, the eiectoi' the` brakes on the stability of the tandem system is intermediatethat of the wheel brakesand that of the transmission brake. When thebraking effort is moderate, however, the danger of turning overthetandem system is slight. f

1f the braking errori' is increased ui the point -of locking' allbrakes, the grader is abruptly decelerated and the force of inertia.acting on the driving axle becomes very large. The danger is bypassed bya return valve 62. Leverils connected with the parking brake lever 43 ofturning over the tandem system lthen increases, but conditions becomediierent from those considered above. The locked wheel brakes preventthe tandem system from rotating about any axis other. than the axispassing through the points of contact of wheels I with the ground. Thelocked transmission brake prevents the tandem system from rotating aboutany other axis than the axis above denned depending on the sprocket.ratio. These two restraints completely immobilize the tandem system withrespect to the vehicle frame even if the braking effort reaches asumcient value to cause the wheels to.slip on the ground. Any. danger ofthe tandem system turning over is thereby completely removed, and themoldboard remains at its preadjusted height during application of thebrakes regardless of the magnitude of the braking efforts.

When the vehicle is traveling backwards, braking tends to cause thetandem system to rock in the reverse direction about wheels I1 insteadof wheels I6, but locking of the transmission brake and of the wheelbrakes again prevents any rocking of the tandem system. This result isobtained regardless of Whether the Wheels be running on the ground or ona flexible or articulated track. It is also obtained in vehiclesprovided with a single pair of driving wheels mounted on wheel armspivoted on. the vehicle frame and held in stable position by means ofsprings instead of by a second pair of wheels.

- In this case, rocking of the wheel arms always takes place about thesame pair of wheels, but the wheel arms again tend to'rotate in adirection depending on the direction of travel of the vehicle. In eachcase, the desired result may be obtained by providing a brakeacting'between the propulsion system of the vehicle and the vehicleframe, and another brake acting between the propulsion system and thewheel arms as in the above described embodiment. .Either brake may alsobe used in combination with a brake acting between the wheel arms andthe frame. In any case, it is immaterial whether the engine be mountedon the frame or on a, separate vehicle.

vThe transmission brake contributesy less than the wheel brakes to thetendency of the tandem system to turn over because it tends to cause theturning over to take place about a higher axis. From that point of Viewit would be advantageous to apply the major portion of the braking eortto the transmission brake. On the other hand, the transmission brakeacts through the iinal drive, which is thereby subjected to considerablestresses. The braking efforts are therefore prei'- erably appliedlargely through the wheel brakes, and it has been found advantageous toapply onethird of the braking effort through the transmission brake andthe remaining two-thirds through the wheel brakes.

' of the driving wheels on the ground and the transmission brake aloneshould preferably be able to exert a braking eiiort greater than themaximum tractive eiort of the engine;

If it is desired to avoid transmitting braking efforts through the nnaldrive except in emergencies, valves 6l and 52 are inserted in piping 51between cylinder 55 and master cylinder 41. 75

When a moderate pressure is exerted on brake pedal, valve 5I remainsclosed and only the wheel brakes are actuated to exert a moderatebraking eirort, varying with the pressure applied on the pedal. When thepressure on the pedal is further increased to increase the brakingeffort beyond a predetermined value, the hydrostatic pressure in mastercylinder 41 becomes suiilcient to open valve 5|, which admits brakingnuid into transmission brake cylinder through piping 51. Under theseconditions, all brakes are applied and participate in the brakingeifort. When the brake pedal is released, fluid is returned fromcylinder 55 to the master cylinder throughvvalve 62. Valve 52 beinglightly spring loaded, the fluid in cylinder 55 remains under a. slightpressure suiilcient to prevent leakage of air between piston 55 andcylinder 55 into the braking system.

Whenever the transmission brake is applied hydraulically, lever 55 isrocked about pin 54 and moves yoke 55 towards parking brake lever 53.The yoke slides on rod 54 so that the brake may be applied withoutinterference from the parking brake lever. When the vehicle is to beparked, brake lever 63 is pulled towards the rear. The lever pulls rod54 which engages yoke 55 through nut 56. Lever 53 is again rocked aboutpin 54 to lock the transmission brake alone. Upon rocking of lever 53,piston rod 58 may be withdrawn freely out of contact with piston 55 sothat the transmission brake may be applied without interfering with thewheel brakes or with the hydraulic system.

Although but one embodiment of the present invention has beenillustrated and described, it will be apparent to those skilled in ,theart that various changes and modifications may be made therein withoutdeparting from the spirit of the invention or .from the scope of theappended .l claims. Y

It is claimed andy desired to secure by Letters Patent:

l. In a vehicle, a main wheeled frame, a rigid member pivotally mountedon said frame, a propulsion system for said vehicle comprising anengine, a driving wheel mounted on said member and transmission meansconnecting said engine with said driving wheel, and means fordecelerating said vehicle comprising a first brake acting on saidpropulsion system causing said member to tend to rock about a iirstpredetermined axis, a second brake acting on said propulsion systemcausing said'member to tend to rock about a second predetermined axis,and common means for applying said first and second brakes, whereby saidmember is prevented from rocking when said first and second brakes arelocked.

2; In a vehicle, a main wheeled frame, a rigid member pivotally mountedon said frame, a propulsion system for said vehicle comprising anengine, a driving wheel mounted on. said member and transmission meansconnecting said engine with said driving wheel, and means fordecelerating said vehicle comprising a iirst brake connected betweensaid propulsion system and said frame, a second brake connected betweensaid propulsion system and Asaid member, and common means for applyingsaid first and second brakes.

3. In a vehicle, a main wheeled frame, a rigid member pivotally mountedon said frame, a propulsion system for said vehicle comprising anengine, a driving wheel mounted onsaid member and transmission meansconnecting said engine with said driving wheel, and means fordecelerating said vehicle comprising a first brake Iconnected betweensaid propulsion system and said frame, a second brake connected betweensaid propulsion system and said member, common vehicle comprising a rstbrake connected between said propulsion system and said frame, a secondbrake connected lbetween said propulsion system and said member, andcommon means for applying said rst and second brakes.

5. In a vehicle, a main wheeled frame, a rigid member pivotally mountedon said frame, a propulsion system for said vehicle comprising anengine, a driving wheel mounted on said member and transmission meansconnecting said engine with said driving wheel, and means fordecelerating said vehicle comprising a tlrst brake lconnected betweensaid propulsion system and said frame,` a second brake connected betweensaid propulsion system and said member, brake applying means connectedwith said .second brake to exert an adjustable braking effort, and meansresponsive to increase of said braking effort beyond a predeterminedvalue for operatively connecting said brake applying means with saidilrst brake.

6. In a vehicle, a main wheeled frame, a rigid member pivotally mountedon said frame, a propulsion system for said vehicle comprising anengine, a driving wheel mounted on said member and transmission meansconnecting said en gine with said driving wheel, and means fordecelerating said vehicle comprising a rst brake the friction of saiddriving wheel on the ground,

and common means for applying said, rst and second brakes to'stopsaidvehicle even when said engine is exerting its maximum eilort on saiddriving wheel.

7. In a vehicle, a wheeled frame, a pair oi' tandem cases pivotallymounted on said frame, a propulsion system for said vehicle comprisingan engine, two pairs of driving wheels mounted in tandem on saidcases,and transmission means connecting said engine with said driving wheels,and means for decelerating said vehicle comprising a brake connectedbetween said transmission means and said frame, at least one pair ofbrakes connected between one of said pairs of 'driving wheels and saidtandem cases, and common means for applying the first and second saidbrakes.

8. In a vehicle, a main wheeled frame, apair of tandem cases mounted onsaid frame, a propulsion-system for said vehicle comprising an engine,two pairs of driving wheels mounted in tandem on said cases, andtransmission means connecting said engine with said driving wheels,means for decelerating said vehicle comprising a brake connected betweensaid transmissionmeans and said vframe, at least one pair of brakesconnected 'between one of said pairs of driving wheels and said tandemcasesa brake pedal, 'and a hy.

draulic pressure transmission system connecting said brake pedal withall said brakes for applying all said brakes simultaneously, a., parkingbrake lever, and means comprising a sliding yoke connecting said brakelever with the rst said brake, whereby the rst said brake may be appliedindependently by said brake pedal landv by said brake lever.

9. In a grader, a wheeled frame, Ia moldboard mounted on said frame, apair of tandem cases pivotally mounted on said frame, a'propulsionsystem for said grader comprising `an engine, two

f pairs of driving wheels mounted intandem on said cases, andtransmission means connecting said engine with said driving wheels, andmeans for decelerating said grader while maintaining 1 said moldboard ata substantially constant height comprising va brake connected betweensaid transmission means and said frame, at least one pair of brakesconnected between one of said pairs of driving wheels and said tandemcases, and common means for applying the rst `and second said brakes.

HORACE W. LINDSAY.

